HIGH RESOLUTION PHOTOACOUSTIC SPECTROSCOPY OF THE ...

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36.98 · National Institute of Standards and Technology. Elizabeth Lunny. Last Elizabeth Lunny. 7.58 · California Institute of Technology. Show more authors ...
HIGH RESOLUTION PHOTOACOUSTIC SPECTROSCOPY OF THE OXYGEN A-BAND MATTHEW J. CICH, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA; ELIZABETH M LUNNY, GAUTAM STROSCIO, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA; THINH QUOC BUI, JILA, National Institute of Standards and Technology and Univ. of Colorado Department of Physics, University of Colorado, Boulder, Boulder, CO, USA; CAITLIN BRAY, Department of Chemistry, Wesleyan University, Middletown, CT, USA; DANIEL HOGAN, Department of Applied Physics, Stanford University, Stanford, CA, USA; PRIYANKA RUPASINGHE, Physical Sciences, Cameron University, Lawton, OK, USA; TIMOTHY J. CRAWFORD, BRIAN DROUIN, CHARLES MILLER, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA; DAVID A. LONG, JOSEPH HODGES, Chemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, MD, USA; MITCHIO OKUMURA, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA. NASA’s Orbiting Carbon Observatory missions require spectroscopic parameterization of the Oxygen A-Band absorption (757-775 nm) with unprecedented detail to meet the objective of delivering space-based column CO2 measurements with an accuracy of better than 1 ppm, and spectroscopic parameters with accuracies at the 0.1% level. To achieve this it is necessary for line shape models to include deviations from the Voigt line shape, including the collisional effects of speed-dependence, line mixing (LM), and collision-induced absorption (CIA). LM and CIA have been difficult to quantify in FTIR and CRDS spectra which have been limited to lower pressure measurements. A photoacoustic spectrometer has been designed to study the pressure- dependence of the spectral line shape up to pressures of 5 atm, where LM and CIA contribute significantly to the A-Band absorption. This spectrometer has a high signal-to-noise (S/N) of about 10,000 and frequency accuracy of 2 MHz. In addition, temperature-dependent effects on the line shape are studied using PIDcontrolled cooled nitrogen flow/ heater system. The latest acquired spectra and analysis are reported here.